A scanning nonlinear dielectric microscope (“SNDM”) can be used for observing charge distribution in a semiconductor region, polarization distribution of a dielectric, and the like at a nanoscale level. A measurement sample is two-dimensionally scanned with a probe of the SNDM. However, there can be stray capacitance and a floating inductor, which can lead to disturbance, between the probe and the measurement sample, and between a stage on which the measurement sample is placed and the measurement sample. Since the influence of the disturbance is superimposed on the differential capacitance detected by the probe, measurement sensitivity is lowered, or a measurement value becomes variable.
In addition, when a polishing process, an oxide film forming process, and the like are performed with respect to the measurement sample, there is a case where a surface of the measurement sample is charged. In this case, a charged state of the surface of the measurement sample is changed, and a measured C-V curve is shifted in a voltage direction. Accordingly, a differential capacitance signal detected in the SNDM is changed.
As described above, the SNDM has a feature which can detect a small capacitance change. Therefore, the SNDM is likely to be affected by the ambient environment. Measurement results obtained using the SNDM may vary from day to day even for the same measurement sample and may greatly depend on the ambient environment.